This invention relates to a method and apparatus for orienting a disk (e.g., a silicon wafer) to precisely align a fiducial mark on the disk relative to a reference point external to the disk.
Various processes require the ability to rotationally position a disk to a known orientation. For example, in the fabrication of silicon wafers, in order to mark the disk in a particular location on the disk surface, it is necessary to precisely orient the disk relative to a marking device, e.g., a laser. Such applications may require very precise disk positioning while minimizing any contact with the disk surface. For example, published SEMI guidelines and specifications for silicon wafers used in the production of semiconductor chips appear to require that such wafers be manipulated only by its circumferential edge; see SEMI MI-0298 Specifications For Polished Monocystalline Silicon Wafers, which limits contact to an exclusion zone extending 3 mm from the wafer edge toward its center.